转自：http://blog.csdn.net/yutyliu/article/details/24346459

string t = "";

//整体下载

    IEnumerator downfile(string url, string LocalPath,UILabel DesLable)

    {

        Uri u = new Uri(url);

        HttpWebRequest mRequest = (HttpWebRequest)WebRequest.Create(u);

        mRequest.Method = "GET";

        mRequest.ContentType = "application/x-www-form-urlencoded";

        

        HttpWebResponse wr = (HttpWebResponse)mRequest.GetResponse();

        

        Stream sIn = wr.GetResponseStream();

        FileStream fs = new FileStream(LocalPath, FileMode.Create, FileAccess.Write);

        

        long length = wr.ContentLength;

        long i = 0;

        decimal j = 0;

        

        while (i < length)

        {

            byte[] buffer = new byte[1024];

            i += sIn.Read(buffer, 0, buffer.Length);

            fs.Write(buffer, 0, buffer.Length);

            

            if ((i % 1024) == 0)

            {

                j = Math.Round(Convert.ToDecimal((Convert.ToDouble(i) / Convert.ToDouble(length)) * 100), 4);

                t= "当前下载文件大小:" + length.ToString() + "字节 当前下载大小:" + i + "字节 下载进度" + j.ToString() + "%";

                DesLable.text=t.ToString();

            }

            else

            {

                t = "当前下载文件大小:" + length.ToString() + "字节 当前下载大小:" + i + "字节";

                DesLable.text=t.ToString();

            }

            yield return false;

            

            

        }

        

        sIn.Close();

        wr.Close();

        fs.Close();

        

    }

    string downloadString="已经下载";

      //断点下载

    IEnumerator FPointDown(string uri,string saveFile,UILabel DesLable,UISprite LoadSprite)

    {

        //打开网络连接 

        System.Net.HttpWebRequest request = (System.Net.HttpWebRequest)System.Net.HttpWebRequest.Create(uri);

        System.Net.HttpWebRequest requestGetCount = (System.Net.HttpWebRequest)System.Net.HttpWebRequest.Create(uri);

        long countLength = requestGetCount.GetResponse().ContentLength;

        

        //打开上次下载的文件或新建文件 

        long lStartPos = 0;

        System.IO.FileStream fs;

        if (System.IO.File.Exists(saveFile))

        {

            fs = System.IO.File.OpenWrite(saveFile);

            lStartPos = fs.Length;

            if (countLength - lStartPos <= 0)

            {

                fs.Close();

                t = "已经";

                DesLable.text=t.ToString();

                yield break;

            }

            fs.Seek(lStartPos, System.IO.SeekOrigin.Current); //移动文件流中的当前指针 

        }

        else

        {

            fs = new System.IO.FileStream(saveFile, System.IO.FileMode.Create);

        }

        

        

        if (lStartPos > 0)

        {

            request.AddRange((int)lStartPos); //设置Range值

            print(lStartPos);

        }

        

        //向服务器请求，获得服务器回应数据流 

        System.IO.Stream ns = request.GetResponse().GetResponseStream();

        int len = 1024 * 8;

        

        byte[] nbytes = new byte[len];

        int nReadSize = 0;

        nReadSize = ns.Read(nbytes, 0, len);

        while (nReadSize > 0)

        {

            fs.Write(nbytes, 0, nReadSize);

            nReadSize = ns.Read(nbytes, 0, len);

            t = downloadString+" : " + fs.Length / 1024 + "kb /" + countLength / 1024 + "kb"+"  ----  "+((double)fs.Length/countLength).ToString()+"%";

           

            

            yield return false;

        }

        ns.Close();

        fs.Close();

      //这里放更新安装代码,或者可以测试这个下载的包有没有出错,验证sha和md5